Hugh de Lacy established a manor at Kells that included a castle, likely a motte and bailey fortification, but this early structure was abandoned in 1176 following an Irish attack. Whilst a castle resurfaces in historical records from 1212, its exact location and what became of it remain unknown. The medieval defensive structure seems to have vanished from history, leaving only tantalising mentions in old documents.

By 1663, a rather different castle stood at the southern end of Maudlin Street, now Castle Street. This three-storey stone and lime structure, complete with a vault, was known locally as the Thoulsell. Rather than serving as a military fortress, this building appears to have been designed for civic purposes; it likely functioned as a town hall and market house at the heart of Kells’ commercial centre. By the early eighteenth century, it had been repurposed as a courthouse. Estate maps from 1762 and 1817 show this castle occupying an island site surrounded by streets, directly opposite the Market Cross.

Early nineteenth-century illustrations reveal an intriguing building: an oblong block of two or three bays and two storeys, distinguished by a circular corner tower on Market Street. This tower, probably housing a staircase, featured machicolations on its parapet and was topped with a high conical roof. The castle had been modernised over time, with large rectangular sash windows inserted under brick relieving arches, and a lintelled doorway added within a round-arched surround at the tower’s base. Despite trees growing on its parapet by the early 1800s, the building remained occupied, though its condition had clearly deteriorated. By the 1830s, when the Ordnance Survey mapped the town, this curious civic castle had been demolished, ending centuries of castle presence in the heart of Kells.